PVMBG reported that the eruption at Semeru continued during 2-8 March, causing the observatory to issue several VONAs mostly for ash plumes. Ground observers noted an ash plume at 0540 on 3 March that rose vertically 4.2 km above the summit. At 2004 later that day a pyroclastic flow originating from the end of a lava flow descended the Kobokan drainage on the SE flank; an ash plume was not visible. Ash plumes at 0742 on 5 March, and at 0603 and 0734 on 6 March, rose 400-500 m above the summit and drifted N and NW. Ash plumes at 0534 and 0735 on 7 March rose 1 km and drifted SSE and NW, respectively. More ash plumes at 0541 and 0758 on 8 March rose 400 m and drifted SW and S. The Alert Level remained at 3 (on a scale of 1-4). The public was warned to stay at least 500 m away from Kobokan drainages within 17 km of the summit, along with other drainages originating on Semeru, including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

Geological Summary. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)